Considerable research has been conducted recently in the area of producing alkenes for use as industrial raw materials. Among the many uses of such commodity chemicals include plastics and fibers for consumption in packaging, transportation and construction industries. Of particular interest are areas of research focusing on production of alkenes, such as ethylene, which is consumed principally in the manufacture of polyethylene and substituted alkanes, such as ethylene dichloride and vinyl chloride. Ethylene is also employed in the production of ethylene oxide, ethyl benzene, ethylene dichloride, ethylene-propylene elastomers and vinyl acetate.
The primary sources of alkenes, such as ethylene, include: steam cracking of organics, such as gas oils; off-gas from fluid catalytic cracking (FCC) in oil refineries; catalytic dehydration of alcohols; and recovery for coal-derived synthesis gas. However, the worldwide demand for alkenes is extraordinary: the shortfall in worldwide supply of ethylene alone was estimated in 1991 to be about 2.3 million tons, as determined by the Chemical Economics Handbook, SRI International (1992). Further, known methods for producing alkenes have significant drawbacks. For example, all of these methods are limited to partial decomposition of organics to lower molecular weight compounds. Also, organic steam cracking, which accounts for about 100% of ethylene production in the United States, is a mature technology which is highly sensitive to process variables, such as cracking severity, residence time and organic partial pressure, as well as plant economics and price fluctuation. In addition, such processes are facing increasing environmental regulatory pressure to control systemic problems, such as leaks and failure from related equipment, and safety concerns associated with olefin cracking.
Other listed production methods have even greater limitations. The availability of FCC off-gas, for example, generally prohibits its use as an economically viable feedstock. Catalytic dehydration of alcohols are effectively limited to certain countries that have large amounts of readily available fermentation raw material. Also, known methods for production of alkenes from other sources, such as coal and coal-derived naphtha and methanol, are, at best, only marginally commercially viable.
Therefore, a need exists for an improved method of producing alkenes which significantly reduce or eliminate the above-mentioned problems.